Sommerdijk and Stevels in an article entitled "The Behavior of Phosphors with Aluminate Host Lattices," Philips Technical Review, 221-233 (1977), discuss lanthanum aluminates and cerium aluminates. The article reports the existence region for the cerium aluminates and lanthanum aluminates with the formulae (La.sub.0.86 O.sub.0.14)Al.sub.11.9 O.sub.19 and (Ce.sub.0.86 O.sub.0.14)Al.sub.11.9 O.sub.19, respectively, as being "fairly narrow". The article further includes a discussion of a series of compositions represented by the formula (La.sub.1-x Ce.sub.x).sub.0.86 Al.sub.11.9 O.sub.19.14.
In a later article entitled "Ce.sup.3+ Luminescence in Hexagonal Aluminates Containing Large Divalent or Trivalent Cations," J. Electrochem Soc. 125, 588-594 (1978), Stevels discusses the luminescent properties of the (La.sub.1-x Ce.sub.x).sub.0.86 Al.sub.11.90 O.sub.19.14 series. The luminescence spectra of the compositions are reported to display two bands: one having a maximum in 330-350 nm region and the other with a maximum in the 410-430 nm region.